This invention relates to hose repair and more particularly to a method and apparatus for joining two segments of flexible hose by splicing to form a continuous long length hose. More specifically, this invention relates to an improved method and apparatus particularly suitable for field splicing operations.
Presently in the repair of hose, and more particularly to field splicing large bore hose such as irrigation hose, it is the practice to use splicing materials that do not require vulcanization, i.e., that are precured and ultimately bonded to the primary hose components by means of a chemical bond or adhesive system. This type splicing operation eliminates having to ship long lengths of hose to facilities that have vulcanization equipment available so that the splice may be cured into an integral structure with the hose components. However, such non-vulcanizing operations have not been completely successful in high pressure systems because of failures in the adhesive bond.
Further, it is the present practice to insert a mandrel into the hose bore at the juncture of the abutted ends to be spliced, so that the splicing materials may be applied without having the hose collapse. These mandrels are generally of a solid metal construction or they may also comprise an inflatable membrane and associated inflating apparatus that serve to support the splicing area. In either case, the mandrel must be removed from the hose bore upon completion of the splicing operation. Various techniques for removing the mandrel are disclosed in the art and these include (a) blowing it out by water or air pressure, (b) using an external electromagnetic device to draw the metal mandrel or other associated metallic apparatus out of the bore, and/or (c) attaching cables or the like to the mandrel to pull it out of the hose bore.
For hose lengths of 50 ft or less, removal of the mandrel poses no particular problem, however, for very long lengths on the order of hundreds of feet, insertion and removal of the mandrel is a problem that is not easily solved by present techniques. For example, irrigation hose in excess of 600 ft may be stored or wound on large spools and in this circumstance the hose must be unwound and laid out full length such that the mandrel removal apparatus may be inserted and the mandrel may later be removed by one of the beforementioned techniques.
The intent of the present invention, therefore, is to provide a method and apparatus for splicing hose wherein the splicing components are integrally vulcanized to the primary hose components to form a unitary structure that will withstand internal stresses to which the hose is subjected during service. The invention further provides a unique assemblage of apparatus for splice fabrication that are readily applied to field splicing operations and wherein the mandrel is easily removed from extremely long lengths of hose without resort to high pressure fluid, electromagnetic devices, and/or cables and the like.
In this respect the method of the invention comprises removing the covering material for a length "L" from each hose end to expose the underlying reinforcement fabric; preparing the ends by buffing the bore of the liner tube and the hose covering for a length L' and cleaning the buffed areas with an appropriate solvent; winding a length of an uncured sealing elastomer about the midpoint of a cylindrical plaster mandrel, the mandrel characterized by an annular concave groove at its midpoint with the sealing elastomer filling the groove to the outer surface of the mandrel with the circumference thereof being substantially equal to the bore circumference of the hose being spliced when positioned on the mandrel; inserting the mandrel into each hose end bore such that the ends are in an abutting relationship at the approximate midpoint of the mandrel in the area of the sealing elastomer; filling the juncture of the abutted ends with an uncured elastomeric packing for the depth of the hose liner tube and the reinforcement fabric to fill any gaps that may exist therebetween due to a mismatch of the ends; wrapping the juncture of the abutted ends with a reinforcement textile fabric material having uncured elastomeric gum on both surfaces to provide a bond with the underlying hose reinforcement for the length 2L of the exposed hose reinforcement; wrapping an uncured elastomeric cover about and completely covering the reinforcement textile fabric for the length 2L and extending an additional length in either longitudinal direction to overwrap the existing hose cover for the length L' such that the overall covering has a width of at least 2L+2L'; wrapping a nylon cure tape about the splice area in a first direction overlapping at least half the width of the tape and doubling back in the opposite direction such that the double overlap results in at least four thicknesses of the tape across the width of the splice; wrapping the splice area with a heat tape and connecting the tape to a source of electrical power to provide sufficient heat to vulcanize the underlying splice components; and removing the heat and cure tapes upon completion of the vulcanization and breaking up the plaster mandrel within the hose so that it may be washed out under normal fluid pressure.